Temperature-responsive sonic oscillator

ABSTRACT

A temperature sensor of the fluidic oscillator type comprising a housing enclosing a chamber having an inlet aligned with an axis and an outlet configured to facilitate choked flow therethrough. The sensor includes a divider element separating the chamber into two subchambers, each having its maximum dimension substantially parallel to the inlet axis. The divider element is provided with a knife edge oriented toward and separated from the inlet. Means may also be included for directing a portion of the fluid whose temperature is to be measured along outside surfaces of the housing to provide improved transient response.

United States Patent Inventor Appl. No.

Filed Patented Assignee Gary L. lnnes Brooklyn Park, Minn. 801,429

Feb. 24, 1969 Apr. 27, 1971 Honeywell Inc., Minneapolis, Minn.

TEMPERATURE-RESPONSIVE SONIC OSCILLATOR 10 Claims, 6 Drawing Figs.

US. Cl

Int. Cl Fl5c 1/08,

Field of Search References Cited UNITED STATES PATENTS 3,294,103 12/1966Bowles Fl5c A/OO 137/815 3,398,758 8/1968 Unfried 137/815 3,451,4116/1969 Johnson 137/815 3,468,331 9/1969 ONeal 137/815 PrimaryExaminer-William R. Cline Att0rneys-CharleS J. Ungemach and Charles L.Rubow ABSTRACT: A temperature sensor of the fluidic oscillator typecomprising a housing enclosing a chamber having an inlet aligned with anaxis and an outlet configured to facilitate choked flow therethrough.The sensor includes a divider element separating the chamber into twosubchambers, each having its maximum dimension substantially parallel tothe inlet axis. The divider element is provided with a knife edgeoriented toward and separated from the inlet. Means may also be includedfor directing a portion of the fluid whose temperature is to be measuredalong outside surfaces of the housing to provide improved transientresponse.

PATENTED Amman 3575; 191

FIG. 5

INVENTOR. 25 GARY 1L. INNES w War/7 ATTORNEY TEMPERATURE-RESPONSIVESONIC OSCILLATOR BACKGROUND OF THE INVENTION This invention relatesgenerally to fluid-handling apparatus, and more specifically, to fluidicdevices responsive to temperature.

Temperature-sensitive fluidic oscillators, particularly of the sonicoscillator type, have recently provided great improvements in the art ofrapidly and accurately measuring very high temperatures. For the purposeof this specification, a sonic oscillator will be defined as one whichoperates on the edge-tone effect. Such an oscillator typically comprisesa nozzle for issuing a fluid jet which impinges on a knife edge. If thenozzle-knife edge arrangement is properly dimensioned, the fluid streamwill oscillate about the knife edge at a frequency dependent on theproperties (temperature) of the fluid in the stream. Resonant chambersmay be provided on one or both sides of the knife edge to enhance theoscillation.

One of the more serious problems with existing fluidic temperaturesensors relates to transient response lt has been found that thetransient response of a device of this type reflects two time constants.The first time constant is dependent on the time required to exchangethe fluid within the sensor. The second is dependent on the timerequired to bring the sensor housing to its final steady statetemperature. The resonant frequency of the resonant chamber or chambersis dependent on dimensions of the chambers and the properties(temperature) of the fluid therein. The time required for the resonantfrequency to change is affected by the purging (exchange) time of thechambers, the thermal inertia of the sensor body and the rate of heattransfer therefrom. In priorart fluidic temperature sensors, the firstand second time constants typically have values of 10 milliseconds and 1minute respectively. Upon application of a step temperature input, theindicated temperature will reach approximately 60 percent of its steadystate value in about 40 milliseconds (four time constants). Thereafter,the indicated temperature will require approximately 3 minutes to comewithin a few percent of its final steady state value.

Another problem with prior-art fluidic temperature sensors relates tosensor size. A controlling dimension in sensors of this type is thedistance between the inlet nozzle and the knife edge. This dimensioncannot be reduced to less than some minimum value for optimum operation.Further, the mean operating frequency of the sensor is a function of thedimensions of the resonant chambers. For typically required operatingfrequencies, a characteristic dimension of each chamber (length) issubstantial (for example, 1 inch). In the more satisfactory prior-artsensors, the resonant chambers have been axially aligned on oppositesides of the nozzle-knife edge arrangement. Thus, all of the outersensor dimensions have fixed minimum values. These dimensions have beenfound too large for many applications, as for example, temperatureprobes for insertion into the combustion chamber of certain gas turbineengines.

A further problem with prior-art fluidic temperature sensors relates todifficulty of construction from high-temperature materials. Even thoughthese sensor configurations are relatively simple, they are sufficientlycomplex that the cost of fabrication from high-temperature materials,such as silicon carbide, is not attractive.

The applicant has provided a unique fluidic oscillator temperaturesensor configuration which overcomes the above-described problemsassociated with prior-art fluidic temperature sensors. Specifically, theapplicants unique temperature sensor is of very simple construction, issmall in size, and provides greatly improved transient response.

SUMMARY OF THE INVENTION Briefly, the applicant's invention comprises atemperaturesensitive fluidic oscillator including an inlet nozzle forissuing a fluid stream which impinges on a knife edge anda pair ofchambers on opposite sides of the knife edge, each chamber having itsmaximum dimension substantially parallel to the axis with which thenozzle-knife edge is aligned. Nozzle means configured to promote chokedflow is provided for exhausting fluid from the chambers. Means may alsobe included for directing a portion of the fluid whose temperature is tobe measured along outside surfaces of the sensor housing to improvetransient operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded view of theapplicant's unique temperature sensor showing its basic elements;

FIG. 2 is a plan view of a component part of the applicants sensor takenalong lines 2P2 in FIG. 1;

FIG. 3 illustrates one embodiment of the applicant's unique temperaturesensor as assembled from. the parts shown in FIG.

FIG. 4 illustrates an embodiment of the applicants unique temperaturesensor including an insulated jacket, pickoff means and fluid signalutilization means;

FIG. 5 is an end view of the sensor embodiment of FIG. 4 taken alonglines 5-5; and

FIG. 6 is an end view of the sensor embodiment shown in FIG. 4 takenalong lines 6-6, showing alternate pickoff means and a simplifiedcircuit responsive to the pickoff output.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 3, referencenumeral 10 generally identifies one embodiment of the applicant's uniquetemperature sensor. Sensor 10 basically comprises a pair of housingmembers 11 and 12 and a divider element 13. FIG. 1 is an exploded viewof these parts in which they are identified by the same referencenumerals. A plan view of member 12 is shown in FIG. 2 which, taken incombination with FIG. 1, clearly illustrates its interior details.

Members 11 and 12 are of identical geometry. Therefore, only member 12will be described in detail. Member 12 basically comprises a shellhaving a cavity 15 therein. Cavity 15 includes a first portion 16 whichis shown as a cylindrical hollow of rectangular cross section alignedwith an axis 17.

- Cavity 15 further includes a second portion 18 also shown as having arectangular cross section and aligned with axis 17. Portion 18, however,is of converging-diverging geometry along axis 17. Member 12 alsoincludes a channel 19 which extends from portion 16 of cavity 15 to theoutside of member 12.

Divider element 13 basically comprises a flat plate of sufficient lengthand width to cover the cavity and channel in member 12. Divider element13 is provided with an opening 20 therethrough at one end. The wallbounding opening 20 opposite its open end is formed into a knife edge21.

As shown in FIGS. 1 and 3, member 12 and member 11, which is identicalto member 12, are assembled with their open sides oriented one towardthe other. Thus, member 11 and 12 basically define a cylindricalchamber. Divider element 13 is sandwiched between members 11 and 12 withthe opening therein positioned away from portion 18 of cavity 15.Members 11 and 12 and divider element 13 cooperate to form an inletnozzle 25 aligned with a central axis 26. Although not shown in FIG. 3,it is apparent that knife edge 21 forms a splitter element also alignedwith and intersecting axis 26. Divider element 13 further separates thecylindrical chamber defined by members 11 and 12 into two substantiallyequal cylindrical subchambers, each having its maximum dimensionsubstantiallyparallel to axis 26. Portion 18 of cavity 15, and thecorresponding portion in member 11 form convergingdiverging outletnozzles communicating with the subchambers in members 11 and 12. Channel19, when covered by divider element 13, forms a signal pickofi passagefor use with nonfluidic (no flow) pressure transducers.

For, reasons which will hereinafter be discussed, it is desirable tomake the walls of members 11 and 12 as thin as possible. For simplicity,members 11 and 12 are shown having basically rectangular cross sections.Further, they are shown as having identical geometries. Accordingly,when members 11 and 12 and element 113 are assembled, two identicalsubchambers, each having an outlet nozzle, are formed. This particularconfiguration is not essential to the applicant's invention. Forexample, the sensor cross section may be round and/or the subchambersneed not be identical. Further, it is not essential that an outletnozzle be provided for each chamber. For purposes of the applicant'sinvention, it is however important that the amount of material in thesensor housing be minimized, that the rate of heat transfer therefrom bemaximized and that the maximum dimensions of the subchambers besubstantially parallel to the inlet nozzle-knife edge axis.

Referring again to FIG. 3, sensor 10 is provided with a mounting flange27 to facilitate its mounting directly in any desired installation, orin an insulated jacket as will hereinafter be described. Since sensor 10is particularly applicable to sensing very high temperatures, it must bespecially constructed to prevent bending and warpage of the sensorhousing due to large thermal gradients therein. Conventionalconstruction techniques, such as bolting, riveting and welding haveproven unsatisfactory under extreme temperature conditions. Suchconstruction techniques are further unsatisfactory in view of the thinhousing walls. Difiusion bonding may, however, be employed to fuse theseparate portions of the housing into a single structure.

It should further be noted that sensor 10 can basically be fabricatedfrom three geometrically simple parts, two of which may be identical.The parts may have rectangular cross sections to simplify machining orother forming operations in high-temperature materials.

Since the minimum transverse dimensions of the housing are not limitedby the minimum allowable spacing between the inlet nozzle and the knifeedge, the housing may have relatively small transverse dimensions. Thisconfiguration allows the sensor housing to be made from a minimum amountof material, thus minimizing its thermal inertia. Further, the smallsize of the sensor permits it to be built into a probe which can, forexample, be easily inserted into the combustion chamber of a gas turbineengine. In such an installation, the gas whose temperature is to bemeasured flows both outside and inside the sensor housing, thussubstantially increasing the rate of heat transfer therefrom. Reducingthe amount of material in the sensor housing and increasing the rate ofheat transfer therefrom substantially decreases the second time constantin the transient sensor response. For example, whereas the second timeconstant associated with a typical prior-art fluidic temperature sensoris in the order of 1 minute, the second time constant associated withthe applicants present temperature sensor is in the order of 6-8seconds. Accordingly, the applicant's temperature sensor offers greatlyimproved transient performance.

In applications where internal installation is not feasible ordesirable, the fluid whose temperature is to be measured may be broughtto the sensor, and alternate means provided for directing a portion ofthe fluid along outer surfaces of the sensor housing. Such means forimproving the sensor transient response is shown in FIGS. 4, 5 and 6 inwhich the elements of the sensor shown in FIGS. 1, 2 and 3 areidentified by like reference numerals. In FIG. 4, reference numeral 30identifies a tubular jacket surrounding sensor 10 and mounted onmounting flange 27. Jacket 30 includes a fluid inlet 31 which is alignedwith inlet nozzle 25. Fluid outlets 32 outside housing members 11 and 12are provided in mounting flange 27. Jacket 30 is spaced from the housingof sensor ll) so as to provide fluid flow paths between inlet 31 andoutlets 32 along surfaces of the sensor housing.

It will be noted that outlets 32 are relatively small. This provides fora positive pressure on the outside of the sensor housing. A slightpositive pressure on the outside of the sensor housing is desirable,particularly if the housing walls are very thin, to prevent distortionof the housing and/or rupture of the bonded joints which would introduceerrors into the sensor output signal.

A portion of the fluid entering inlet 31 also enters inlet nozzle 25.The fluid entering inlet nozzle 25 impinges on knife edge 21 andthereafter flows through the subchambers and exhausts through exhaustnozzles 33 and 34. Nozzles 33 and 3d, which are formed by portion 18 ofcavity 15 in housing member 12 and the corresponding cavity portion inhousing member 11, are configured so as to provide choked flowtherethrough with a minimum total pressure differential across thesensor. Choked flow through exhaust nozzles 33 and 34 is desirablebecause the pressure ratio across the inlet nozzle 25 is then constantand the sensor is thereby made insensitive to variations in the totalpressure difierential thereacross. The frequency of the sensor outputsignal is thus relatively independent of variations in pressure in thefluid supplied thereto.

It is frequently desirable to use sensor 10 directly in a fluidic systemcomprising conventional fluidic devices. Such devices require fluidsignals having controlled low means pressure levels. Further, theoscillating signal must be extracted from sensor 10 without creatingflow parallel to the exhaust nozzle flow since such parallel flow woulddisrupt the choked flow operation. This function may be accomplished bymeans of a quarter wave resonator 35 which communicates with exhaustnozzle 33 and is shown attached to mounting flange 27. Resonator 35 istuned to the same frequency as the subchambers within sensor 10 andserves to enhance the oscillating signal transmitted thereinto. It willbe noted that one of outlets 32 also terminates within resonator 35.This serves to mmntain the fluid in resonator 35 at a temperature whichapproximates the temperature of the fluid entering sensor 10.Accordingly, the resonant frequency of resonator 35 is maintained nearthe resonant frequency of the subchambers for all temperatures of thefluid entering sensor 10.

It should be noted that although a quarter wave resonator is shownemployed with sensor 10, other acoustically active control volumes arealso equally suitable. For example, an open resonator having a lengthequal to any odd integral multiple of the quarter wave resonator lengthmay be used. For purposes of this specification, an acoustically activecontrol volume is defined as a volume which, because of its geometricdimensions amplifies a specific frequency spectrum and attenuates otherfrequencies.

A pickoff tube 36 is provided in communication with resonator 35 andserves to separate the acoustic intelligence, in the form of anoscillating signal, from the bulk fluid flow through the resonator. Theoscillating signal in pickoff tube 36 may be transmitted to any suitableutilization device, normally a fluidic network, which is identified byreference numeral 37 in FIG. 4.

In other applications it may be desirable to employ sensor 10 directlywith electronic utilization apparatus This can be accomplished as shownin FIG. 6 by making use of channel 19 which leads from the subchamberwithin member 12 to the outside of the sensor housing A large-magnitude,high-quality signal may be extracted through channel 19 by means of aninfinite impedance (zero flow) electrical transducer. Reference numeral38 identifies such a transducer which converts the oscillating pressuresignal into an oscillating electrical signal having the same frequency.The electrical signal is amplified by means of amplifier 39 andtransmitted to an electronic counter 40. Counter 40 then displays thefrequency of the oscillating pressure signal produced by temperaturesensor 10. This frequency is accordingly indicative of the temperatureof the fluid within sensor 10. This electronic utilization apparatus isintended to be exemplary only. Many other forms of such apparatus areequally suitable.

It will be apparent that there may be substantial heat loss throughjacket 30. If so, the temperature of the fluid flowing along thesurfaces of sensor 10 will be lowered, which will in turn lower thehousing temperature of sensor 10 and impair the accuracy of the outputsignal produced thereby. Heat loss through jacket 30 can be reduced bysurrounding it with thermal insulation which is identified in FIGS. 4and 5 by reference numeral 41. Jacket 30 and insulation 41 serve tomaintain the excellent accuracy and fast time response of sensor ininstallations in which the sensor cannot be mounted directly in thesource of fluid whose temperature is to be measured.

Iclaim:

1. Temperature-responsive apparatus of the sonic oscillator typecomprising:

housing means defining a substantially cylindrical chamber and an inletnozzle aligned with a central axis, said housing means including adivider element aligned with a central axis and dividing the chamberinto first and second substantially equal cylindrical subchamberslongitudinally aligned respectively with first and second axes, thefirst and second axes each parallel to and spaced from the central axis,the divider element having a knife edge intersecting the central axis,oriented toward the inlet nozzle and spaced from the inlet nozzle by adistance suitable for achieving edge-tone oscillation of a fluid streamfrom the inlet nozzle about the knife edge, said housing means furtherdefining first and second outlet nozzles configured to promote chokedflow therethrough, said first and second outlet nozzles communicatingrespectively with the first and second subchambers.

2. The apparatus of claim 11 further including signal pickoff meanscomprising an acoustically active control volume in communication with asubchamber in said housing.

3. The apparatus of claim 1 including transient response improvementmeans comprising a jacket surrounding said housing means, said jackethaving an inlet substantially aligned with said central axis and outletmeans remote from said inlet, said jacket being spaced from said housingso as to provide fluid flow paths along outer surfaces of said housing.

4. The apparatus of claim 3 wherein thermal insulation is providedaround outer surfaces of said jacket.

5. Fluid-responsive apparatus of the sonic oscillator type comprising:

housing means enclosing a chamber having an inlet nozzle aligned with anaxis and an outlet nozzle configured to promote choked flow; and

a divider element located within the chamber and aligned with said axisso as to separate the chamber into subchambers, each subchamber havingits maximum dimension substantially parallel to said axis, said dividerelement having a knife edge oriented toward and spaced from said inletnozzle by a distance suitable for achieving edge-tone oscillation of afluid stream from the inlet nozzle about the knife edge.

6. The apparatus of claim 5 including transient response improvementmeans for directing a fluid whose temperature is to be measured intosaid inlet nozzle and along outer surfaces of said housing.

7. The apparatus of claim 6 wherein said transient response improvementmeans comprises a jacket surrounding said housing means, said jackethaving an inlet substantially aligned with said axis and outlet meansremote from said inlet, said jacket being spaced from said housing so asto provide fluid flow paths along outer surfaces of said housing.

8. The apparatus of claim 5 further including signal pickoff means incommunication with a subchamber in said housing and means connected tosaid signal pickoff means responsive to signals produced thereby.

9. The apparatus of claim 8 wherein said signal pickoff means comprisesan acoustically active control volume in communication with a subchamberin said housing.

110. The apparatus of claim 8 wherein said signal pickoff meanscomprises an electrical pressure transducer in communication with asubchamber in said housing.

1. Temperature-responsive apparatus of the sonic oscillator typecomprising: housing means defining a substantially cylindrical chamberand an inlet nozzle aligned with a central axis, said housing meansincluding a divider element aligned with a central axis and dividing thechamber into first and second substantially equal cylindricalsubchambers longitudinally aligned respectively with first and secondaxes, the first and second axes each parallel to and spaced from thecentral axis, the divider element having a knife edge intersecting thecentral axis, oriented toward the inlet nozzle and spaced from the inletnozzle by a distance suitable for achieving edge-tone oscillation of afluid stream from the inlet nozzle about the knife edge, said housingmeans further defining first and second outlet nozzles configured topromote choked flow therethrough, said first and second outlet nozzlescommunicating respectively with the first and second subchambers.
 2. Theapparatus of claim 1 further including signal pickoff means comprisingan acoustically active control volume in communication with a subchamberin said housing.
 3. The apparatus of claim 1 including transientresponse improvement means comprising a jacket surrounding said housingmeans, said jacket having an inlet substantially aligned with saidcentral axis and outlet means remote from said inlet, said jacket beingspaced from said housing so as to provide fluid flow paths along outersurfaces of said housing.
 4. The apparatus of claim 3 wherein thermalinsulation is provided around outer surfaces of said jacket. 5.Fluid-responsive apparatus of the sonic oscillator type comprising:housing means enclosing a chamber having an inlet nozzle aligned with anaxis and an outlet nozzle configured to promote choked flow; and adivider element located within the chamber and aligned with said axis soas to separate the chamber into subchambers, each subchamber having itsmaximum dimeNsion substantially parallel to said axis, said dividerelement having a knife edge oriented toward and spaced from said inletnozzle by a distance suitable for achieving edge-tone oscillation of afluid stream from the inlet nozzle about the knife edge.
 6. Theapparatus of claim 5 including transient response improvement means fordirecting a fluid whose temperature is to be measured into said inletnozzle and along outer surfaces of said housing.
 7. The apparatus ofclaim 6 wherein said transient response improvement means comprises ajacket surrounding said housing means, said jacket having an inletsubstantially aligned with said axis and outlet means remote from saidinlet, said jacket being spaced from said housing so as to provide fluidflow paths along outer surfaces of said housing.
 8. The apparatus ofclaim 5 further including signal pickoff means in communication with asubchamber in said housing and means connected to said signal pickoffmeans responsive to signals produced thereby.
 9. The apparatus of claim8 wherein said signal pickoff means comprises an acoustically activecontrol volume in communication with a subchamber in said housing. 10.The apparatus of claim 8 wherein said signal pickoff means comprises anelectrical pressure transducer in communication with a subchamber insaid housing.